The genetic basis for relationship among red blood cell antigens, isoenzyme types and physiological function will be studied. The relationships among genes in pigs which are associated with susceptibility to the porcine stress syndrome (PSS) will be used as a model. Expression of PSS as identified by development of muscular rigidity under halothane anesthesia is associated with blood factors in the H system of red blood antigens and with PHI (phosphohexose isomerase) isoenzyme types, but the associations are not entirely consistent from population to population. There is close linkage between genes from H and PHI types, and these genes are also linked to genes for 6PGD (6-phosphogluconate dehydrogenase) isoenzyme types. Recombination among genes for H, PHI, 6PGD and halothane types will be measured among offspring from appropriate matings. Isoimmunizations will be made to develop reagents for new red cell antigenic factors.